The present invention relates to a lumped element circulator for use in the microwave frequency region.
A microwave circulator is a device useful for interconnecting microwave components. It can be used as an isolator for aiding in matching microwave components so that reflected signals do not interfere with transmission. A conventional lumped element microwave circulator is advantageous because of its reduced construction. It comprises a dielectric substrate and a ferromagnetic substrate which is formed on a metallized surface of the dielectric substrate. A set of three overcrossing pairs of parallel conductive strip lines extend across the ferromagnetic substrate with 120 degrees angular separation from each other, each end of the pairs being short-circuited. One end of each strip line pair is connected by a first coupling lead to one of a plurality of capacitors and thence to an associated input/output port and the other end of each strip line pair is connected by a second coupling lead to the metallized surface of the dielectric substrate. Resonance is established by each strip line pair and the associated capacitor.
However, the conventional lumped element circulator is still not satisfactory in terms of its operating frequency range. Broadband lumped element circulators capable of high frequency operation are desired for use in a variety of applications.